"Most of the time, multitasking is an illusion. You think you are multitasking, but in reality you're actually wasting time switching from one task to another." ~ Bosco Tjan

So many people -- especially Millennials -- believe multitasking is a skill they have perfected and will proudly proclaim how much more effective they are because of it. Sadly, the opposite is true in reality.

Despite how multitasking is perceived, empirical research shows us again and again that it actually decreases effectiveness. In one study, participants were asked to do tasks in a serial manner, which meant they had to complete one task before moving on to the next. Their effectiveness was compared to multitasking participants who did a little bit of the first project, then a little bit of the second, until both tasks were complete. Results showed the multitasking group was 65% as effective as the serial group.

Recently, Stanford completed a study with 262 students who believed their ability to multitask enhanced their performance. Again, this study confirmed multitasking is less effective than doing one task at a time since the brain can only focus on one thing at a time.

Another finding of the Stanford study was that multitaskers were much less effective than non-multitaskers when they were asked to do one task at a time. That is to say, the brains of people who regularly multitask just did not operate as efficiently when doing tasks in a serial manner as people who do not multitask.

What is even worse is that the University of London found that multitaskers’ brain activity had been reduced to the level of someone who had stayed up all night or smoked marijuana. Multitasking was found to lower IQ scores by 15 points to the level of an eight-year-old.

I frequently talk about how multitasking makes people less effective, but even I was shocked by the University of London results. From my own experience though, I know that on the rare occasion that I multitask, I do feel exhausted and my thinking becomes very cloudy.

After the University of London released the results of their study, most researchers believed this decline in brain function was temporary and would regenerate after the person had time to rest. Unfortunately, new research out of the University of Sussex found that multitaskers had less density in a certain part of their brains as shown by MRI scans. While more research is needed on this, it raises very concerning questions about the impact of multitasking on the brain.

Putting aside for a minute the possibility that multitasking alters the structure of the brain, consider that multitasking is just like dealing with one interruption after another. Everyone has those days once in a while when they cannot seem to make any progress because they keep getting interrupted. At the end of the day, you feel awful. When multitasking, you are choosing to change your focus, but to your brain, an interruption is an interruption, voluntary or not.

Now go out and try reducing your reliance on multitasking and you will see how much more effective and productive you become.

You can do this.

Jerry Osteryoung is a consultant to businesses - he has directly assisted over 3,000 firms. He is the Jim Moran Professor of Entrepreneurship (Emeritus) and Professor of Finance (Emeritus) at Florida State University. He was the founding Executive Director of The Jim Moran Institute and served in that position from 1995 through 2008. His newest book co-authored with Tim O'Brien, "If You Have Employees, You Really Need This Book," is an Amazon.com bestseller. He can be reached by e-mail at jerry.osteryoung@gmail.com.